I have spent some time on this one and yes, it is difficult.
There are only two trains a day linking Vigo to Porto and these each take +-4hrs:30 min. La Coruna - Vigo by train takes a further 2 hours!
La Coruna is a lot further than Vigo so I really don't think this route is doable by public transport.
If you have a car, the distance is 301km taking about 3:30 mins.
As regards buses there are services from La Coruna to Porto Airport operated by alsa.es
However, the Friday La Coruna to Porto to service operates too late to tie in with the flight from Porto.
On Thursday however, there is a bus from La Coruna Bus Station to Porto Airport leaving at 09:00 arriving 12:30.
There is then a direct flight from Porto to Geneva operated by Easyjet.com as follows
Thursday July 4th
Porto to Geneva
dep. 13:55, arr. 17:00
For the return there is a flight leaving Geneva for Porto as follows:
Sunday July 6th
Geneva to Porto
dep. 13:40, arr. 14:55
However, the current return price is about € 200.
There is a bus from Porto Airport to La Coruna as follows:
Dept Porto Airport 00.45H Arrive La Corunna 06.00H
Easyjet's Summer La Coruna - Madrid service has not yet be confirmed. Not available till 18th May.
It may be that there will be better routings via this route.
However, you might want to have a look at routing via Barcelona although the transit times are somewhat short.
July 4th.
La Coruna to Barcelona - Spanair
09:35 La Coruna 11:10 Barcelona
Barcelona to Geneva
Easyjet
12:05 Barcelona 13:40 Geneva
or
La Coruna to Barcelona - Spanair
15:25 La Coruna 17:00 Barcelona
Barcelona to Geneva - Easyjet
18:05 Barcelona 19:40 Geneva
Sunday, July 06, 2008
Geneva to Barcelona - Easyjet
10:20 Geneva 11:50 Barcelona
Barcelona to La Coruna - Spanair
12:50 Barcelona 14:35 La Coruna
I would suggest that if you can get hold of a car, driving to Porto would probably be the best option.
As regards, rental accomodation in La Coruna, I unfortunately live in the Algarve in the South of Portugal and am not local to La Coruna.
However, if you would like to visit my blog,
http://barlaventostravelblog.blogspot.com/
scroll down to the bottom of the right hand panel, and click on "View my complete profile", you could then click on email and send me your requirements. I will then see if I can assist although it may take some time.